Polyacrylonitrile can be used as a base material for thermochemical conversion into carbon. Especially nanofiber mats, produced by electrospinning, are of interest to create carbon nanofibers. Optimal stabilization and carbonization parameters, however, strongly depend on the spatial features of the original material. While differences between nano- and microfibers are well known, this paper shows that depending on the electrospinning method and the solvent used, considerable differences between various nanofiber mats have to be taken into account for the optimization of the stabilization conditions. Here, we examine for the first time polyacrylonitrile nanofiber mats, electrospun with wire electrospinning from the low-toxic dimethyl sulfoxide as a solvent, instead of the typically used needle electrospinning from the toxic dimethylformamide. Additionally, we used inexpensive polyacrylonitrile from knitting yarn instead of highly specialized material, tailored for carbonization. Our results show that by carefully controlling the maximum stabilization temperature and especially the heating rate, fully stabilized polyacrylonitrile fibers without undesired interconnections can be created as precursors for carbonization.

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Hierarchical porous carbons (HPC) were fabricated from lignin by hard template method using Beta and Y zeolites as templates. Textural properties were dictated by the hard template, obtaining a bi-modal pore size distribution with similar micropore sizes but different mesopore sizes. These HPCs provide a well-connected and developed porosity that show capacitance values near to 140 F g-1 in 1 M H2SO4 at 1 A g-1 and a capacitance retention of ca. 50% and 40% when the specific current is increased from 1 to 64 A g-1 for the Y and the Beta-based carbons, respectively. A symmetric capacitor working at 1.2 V with energy densities of 4.8 Wh kg-1 at 0.5 kW kg-1 has been obtained using the Beta-based HPC. Asymmetric in mass design allowed to operate the capacitor safely at 1.4 V, yielding an energy density of 7.3 Wh kg-1 at 0.5 kW kg-1 , a increase of 50% with respect to the symmetric configuration, while keeping a maximum power of 46 kW kg-1. This capacitor has an energy density comparable to that of a symmetric supercapacitor built using a commercial activated carbon of much higher porosity development, outperforming it in terms of energy, coulombic efficiencies and maximum power.

Electrospinning can be used to create nanofiber mats from diverse polymers which can be used as filters etc. Depending on the spinning parameters, also nano-membranes, i.e. non-fibrous mats, can be produced as well as mixtures from both morphologies. The ratio of membrane to fibrous areas can be tailored by the distance between the high voltage electrode and substrate. Here the impact of the mat morphology on the water vapour permeability through polyacrylonitrile nanofiber mats with different membrane-like areas is shown, allowing for tailoring the permeability between 0.1 Pa · m²/W and more than 10 Pa · m²/W. In this way it is possible to create the finest filters as well as nearly impenetrable thin membranes with the same technology.

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